Split up fs_config_* modules per partition.

This was already done for partitions other than the system partition.
Add new, separate "_system" targets, and add new phony modules which
collects _system and _nonsystem targets for now.

Update the base_system.mk file to only depend on the system module, and
put the other ones in base_vendor.mk for now.

Bug: 80410283
Test: make fs_config_dirs[_*] fs_config_files[_*] and verify output
Change-Id: I7843578dbb9f27edf4c1e5b4a795a530f79e0be1
diff --git a/target/product/base_system.mk b/target/product/base_system.mk
index 66834a3..9db5d43 100644
--- a/target/product/base_system.mk
+++ b/target/product/base_system.mk
@@ -72,6 +72,8 @@
     framework-res \
     framework-sysconfig.xml \
     fsck_msdos \
+    fs_config_files_system \
+    fs_config_dirs_system \
     gatekeeperd \
     healthd \
     hid \